Breech mechanism for a firearm



Dec. 18, 1956 E. M. HARVEY 2,774,283

BREECH MECHANISM FOR' A FIREARM I M Hurvey i' Y /QMMWMM HTTUENEKS E. M. HARVEY BREEZCI-I MECHANISM FOR A FIREARM 4 Sheets-Sheet 2 Filed. June 14, 1954 INVENTOR. Hu rv E y l [j: I .Il Arme/vens INVENTOR. .Hurv E y Trams/sr.;

E. M. HARVEY BREECH MECHANISM FOR A FIREARM Dec. 18, 1956 Filed June 14, 1954v Dec. 18, 1956 E. M. HARVEY 2,774,283

BREECH MECHANISM FOR A FIREARM Y Filed June 14, A1954 4 Sheets-Sheet 4 1N VEN TOR.

@TTU/EVE YS United States Patent BREECH MECHANISM FOR A FIREARM Earle M. Harvey, Agawam, Mass., assignor to the United States of America as represented by the Secretary of the Army Application .lune 14, 1954, Serial No. 436,749

1 Claim. (Cl. 89-194) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates to automatic firearms and especially to the breech mechanisms thereof.

It is an object of this invention to provide an improved breech mechanism for automatic firearms.

It is another object of this invention to provide for automatic firearms a breech mechanism having simplicity of operation and a minimum number of operating parts.

VIt is a further object of this invention to provide for automatic firearms wherein the barrel is xed to the receiver a slidable breech mechanism actuated by a recoiling cartridge case.

It is a still further object of this invention to provide for automatic firearms a gas operated breech mechanism without having the disadvantage of a gas cylinder, piston and gas ports to be fouled or an operating rod to become worn or broken.

It is another and still further object of this invention to provide for automatic rearms a gas operated breech mechanism which utilizes the initial portion of the timepressure curve, which is more uniform from round-toround, for actuation.

It is the specific object of this invention to provide for automatic firearms a breech mechanism which includes a carrier and a bolt member, actuatable to recoil position by a gas recoiled cartridge case and which, during recoil, locks and then unlocks the bolt and moves the same to recoil position for extraction and ejection of the spent cartridge case.

The specicnature of the invention as well as other objects and advantages will clearly appear from -a description of the preferred embodiment as shown in the accompanying drawings in which:

Fig. l is a longitudinal partially cross-sectioned side view of the rear portion of the firearm showing the breech mechanism in battery position; I

Fig. 2 is a View similar to Fig. l but shows the breech mechanism recoiled to locked position by the fired cartridge;

Fig. 3 is similar to the preceding views but shows the bolt carrier in position to unlock the bolt;

Fig. 4 is similar to the preceding views but shows the breech mechanism in recoiled position; and

Fig. 5 is an enlarged perspective exploded view of the breech mechanism shown upside-down.

Shown in the figures is a firearm having a tubular receiver 12 with a barrel 13 fixedly mounted thereto and a magazine 9. Mounted in receiver 12 for slidable longitudinal movement between a battery and a recoil position is a breech mechanism 14 including a relatively massive cylindrical bolt carrier member 15 and a bolt 16. Two pairs of diametrically opposed lugs 17 project from the circumference of carrier 15 to be slidably received in suitable longitudinal slideways in receiver 12 (not shown). A pair of longitudinal holes 19 extend forwardly into carrier 15 to receive the front portions of a pair of driving ice 1 springs 20 arranged to bias breech mechanism 14 to battery position.

The bottom side of carrier 15 is slabbed, as noted at 21, and extending upwardly therefrom is a longitudinal recess 22, arranged to slidably receive bolt 16 as hereinafter noted, and a rearwardly communicating channel 23 which provides clearances for the pivotal swing of hammer 24 into contact with a firing pin 25 slidably mounted in such bolt. Hammer 24 is arranged to be actuated to cocked position by engagement of bolt 16 during recoil ight.

Extending through ring pin 25 is a transverse latch 26 which, as best illustrated in Patent 2,626,474 to JohnL. Lochhead, locks the firing pin in retracted position when bolt 16 is out of battery position, relative to carrier 15. The battery position of bolt 16, relative to carrier 15, is established by the engagement of rearwardly facing shoulders 27 on the bolt with cooperating lugs 28 which extendy from carrier 15 into recess 22.

Extending downwardly from the rear 4bottom portion of bolt 16 is a heel portion 29 having a rear end which is engageable with a lockl abutment 30 in receiver 12 when the bolt has been recoiled a short distance from battery position. In the present embodiment the distance of .085 inch from battery to bolt locked position has been proven satisfactory. Bolt 16 is actuated to recoil position by the rearward projection thereagainst of the cartridge case 42 of a ired cartridge 45 which had been lubricated by a suitable lubricant such as Teon as shown at 18 to facilitate projection of the cartridge case during the eX- plosion. The rear end of bolt 16 is held downwardly to insure engagement of heel portion 29 thereof with lock abutment 39, while carrier 15 continues in recoil-Hight after bolt 16 is locked, by engagement of a bottom side 31 of a transverse rib 32 in recess 22 with the top side of a stepped-down portion 33 at the rear portion of the bolt. When carrier 15 has recoiled to where stepped-down portion 33 is free of bottom side 31, forwardly and upwardly inclining shoulders 35 on each side of the bolt are arranged to engage mating ledges 36 in recess 22 whereby the rear end of bolt 16 is cammed upwardly to disengage heel 29 from locking abutment 30 and to engage carrier 15 for movement to recoil position. The engagement of the inclining shoulders 35 with ledges 36 also support the rear portion of Ybolt 16 during recoil Hight. Bottom side 31 is moved onto the top side of stepped-down portion 33 to move the rear end of bolt 16 downwardly to locked position in counterrecoil by means of a cam 34, which eX- tends upwardly and forwardly from the rear end of bolt 16, engaging the front sloping side 46 of rib 32.

Provided through the forward portion of carrier 15 in longitudinal alignment with lugs 17 is a pair of diametrically opposed holes 37 each of which rotatably receives a guide 38 having an essentially rectangular tongue portion 39 which is slidably received 'by a longitudinally arranged slideway 40 in bolt 16. The engagement of the opposite ends of guide 38 with the inside perimeter of receiver 12 maintains a tongue portion 39 in engagement with slideway 40. An extractor 41 is provided on the forward end of bolt 16 for extracting the spent cartridge case 42 from the chamber of barrel 13 during recoil of bolt 16. A handle 43 extends upwardly from carrier 15 through a slot 44 in receiver 12 for charging the firearm.

Operation When the firearm is in battery, carrier 15 -is pressed forwardly by driving spring 20 and the lugs 28 therein transfer the forward thrust through shoulders 27 to bolt 16 whereby the bolt is pressed against the base of chambered cartridge 45. The actuation of hammer 24 by the operator causes tiring pin 25 to ignite such cartridge and theresulting explosion forces. cartridge. case 42 rearwardly against bolt 16. Case 42 of cartridge 45 had previously been lubricated to. facilitate the projection from barrel 13. Through the engagement oli lugsv 2% and shoulder 27, the recoilimparted to 'bolt 16 is transmitted: to carrier 15A and the two move rearwardly together until heelportion 29- of` holt engages locking abutment 30L in receiver 12. whereupon, bolt 16 is stopped and cartridge case 42 is supported therebyY in the chamber of-y barrel 112 during the remainingtime of the explosion.

While carrier continues in recoil; flight from the inerti-a imparted thereto by the recoiled cartridge case 42, bolt 161 is* maintained inlocked position by the slid'able engagementY of' bottom side 31- of' rib 32 with the topside` ofl stepped-down portion 33. By the time the projectile of cartridge 45J has left the muzzle of barrel 12- and the residual pressure in the bore of the barrel has dropped to a low value, carrier 15 has traveledV to where steppeddownportion 33A is awayY from rib 32J and shoulders 35 in bolt 16 arey engagedlwith ledges 36 of carrier 15- to move heel portion 29 out of engagement Withlock abutment 30 and bolt 16 into engagement with carrier, 15. Consequently, bolt 16 -is accelerated into recoil ight by the inertia of the relatively massive carrier 15 andfthereupon extracts spent cartridge case 42 and cocks hammer 24.

Wheny breech mechanism 14 has been stopped in recoil position, the compressed driving spring 20: drives the breech mechanism forwardly again to strip the leading cartridge'45'- frommagazine 9- and drive thecartridge into the chamber ofbarrelY 13, stopping slightly forward lof lock position as hereinbefore noted.

Fromy the foregoing,` it is clearly apparent that there is here provided'pan improvedl breech mechanism which has theI advantage of gas operated breech mechanisms in the retentionl of xedjbarrel, gun construction, butwhich eliminatesthe disadvantages Vof gas cylinders, pistons and ports that; require frequentV cleaning, 'and which utilizes for the powerstroke the initial portion oftheti'me-pressure c vurve of;l the firearm which, round-to-round, is the most uniform. Further, the breech mechanism of this' invention is distinguishedfor its simplicity.A andruggedness of construction and ease offmanufature.

Althougha particular embodiment of the invention has been described in detailv herein, it is evident that many variations may be devisedwithin the spiritv and; scope thereof and the following claim is intendedto include such variations.

I claim:

In a` firearmv having a receiver andv a barrel with a chamber for a cartridge provided with a projectile and a caserearwardlyprojectable from the chamber whenthe cartridge is fired, a carrier slidablymounted in the receiver for reeiprocation between abattery and 'a recoil position, said carrier beingprovided with a longitudinal recess in the underside'of the front portion'thereofjand oppositelyv disposed holesextending laterally from said recess adjacent? thefront endthereof; a guide rotatably mounted in each one of said holes` and having a tongue portion on the inner end thereof, a bolt received by said recess for longitudinal movement therein, longitudinal recessed guideways in opposite sides of said bolt and adjacent the front portion thereofv for slidably receiving said tongue portions to slidably support the front end of said bolt andl to mount said boltv for pivotal movement of the rear end thereof between a downward lockedposition an upward unlocked position, a head; portion in said, b olt for rearwardly abutting the base of the case to, transfer the recoil force of the case to said bolt for rearward movement thereof, means for transferring the rearward movement of said bolt simultaneously to said carrier for acceleration thereof from said battery position to said recoil. position, asheel portion extendingr downwardly from the rear end of said bolt, a rear portion on said heel portion englageable with a lock abutment in the receiver for stopping saidV` bolt when said bolt is in said'l lock position and whensaidV carrier isenergizedj suiciently for movement to saidA recoil position, a transverse rib extending downwardly fromthe top side off said recess and having an underside and anupwardly andl forwardly sloping surface onY the front side, a cam portion yextending up wardly and forwardly fromsaid' rear end:A of said bolt for engageable cooperationI with said/ sloping surface; to cam said rear end of said= bolt downwardly to saidflockposition for-engagement ofisaid rear endportion onY said heel portion with said locked? abutment, astepped-downportion on the top sidevof saidlboltextendingforwardly from said'- cam portionand being slidably engageable with saidunderside for maintainingsaid rear end portionin engagement'with saidlocked abutmentwhile said carrier continues rearwardly after said bolt is stopped, incliningshoulders disposed. on opposite. sides off said bolt, inclining ledges in-A said recess cooperable with said shoulders for pivoting said rear end of said bolt to-said unlocked position when saidf stepped-'down portiorr isfree of said underside during recoil flightofsaid; carrier for engaging y said bolttossaid carrier-for rearwardmovement-therewith after the projectilehas-left the barrel and'forsupporting said rear end of said bolt ins'aid unlockedposition during movement ofsaid` boltandsaidl c arr-ier together to' said recoil position andA resilient means for returning said carrier to saidbatteryvposition.

References Cited in the le ofthis patent UNITED STATES PATENT/Sw.

998,867 Youngy July 25,1911 1,157,750- You ng` V Oct. 26,1915 1,401,552 Pedersen`I Dec. 27, 19-21 1,517,483 Young Dec. 2, 1924 1,603,684. Garand, v- Oct. 19, 1926. 1,696,537 Kewishi Dec. 25, 1928 2,052,287 End Aug.. 25, 1936 2,144,951 Williams Jan. 24,1939 

